The present invention relates to radiation imaging apparatus and methods. More particularly the present invention relates to radiation imaging apparatus and methods for gamma rays, neutrons, and positron annihilation radiation involving a tubular scintillation body with scintillation sensing units disposed along and around it.
A known type of photon imaging camera is known as the "Anger Scintillation Camera" as described for instance in Nuclear Medicine Physics, Instrumentation, and Agents, by F. D. Rollo, ed., C. V. Mosby Co., St. Louis, 1977, Chapter 6. The Anger scintillation camera employs a planar scintillation crystal with a two dimensional array of photomultiplier tubes (PMTs) arranged thereon. This camera permits a relatively accurate detection of photon event position, but has the crystal and the PMTs moved relative to the specimen in order to produce tomographic images, and images from a variety of directions for other imaging purposes. Moving the delicate apparatus in use is believed to present practical and economic difficulties. This camera receives photons of ionizing radiation from only a limited area in one direction at a time, so it has a relatively low volume imaging efficiency.
Another known type of photon imaging computer tomography apparatus is known as the "HEADTOME II", as described for instance in "A Hybrid Emission CT--HEADTOME II", by Y. Hirose et al., IEEE Transactions on Nuclear Science, Vol. NS-29, No. 1, February, 1982, pp. 520-523. The HEADTOME II as described therein utilizes three detector rings and collimators. Each ring contains 64 rectangular crystals each encapsulated in an aluminum housing and coupled directly to 64 photomultiplers respectively. The detector rings, which include the crystals and photomultipliers, wobble and rotate to achieve a minimum sampling spatial interval for positron study. A rotating collimator is used, and the detector rings also rotate for single photon studies. The rotation, and wobbling, motions are believed to result in practical and economic difficulties similar to those already mentioned in connection with the Anger scintillation camera, but in the HEADTOME II the motion is introduced to obtain accuracy in spatial resolution.
Adapting the known photon imaging devices for imaging of the whole human body increases the difficulties for at least mechanical and structural reasons due to the moving detector parts. The time required to scan the whole body is also increased. The cost of scaling up for whole-body imaging deters the use of known equipment which is already very costly at the smaller scale of imaging body parts.